Between 11th–25th June 2021 (week 7–8 after dose 2), 69 healthcare workers were tested positive for SARS-CoV-2. 62 participated in the clinical study. were (pre)symptomatic with one requiring oxygen supplementation. All recovered uneventfully. 23 complete-genome sequences were obtained. They all belonged to the Delta variant, and were phylogenetically distinct from the contemporary Delta variant sequences obtained from community transmission cases, suggestive of ongoing transmission between the workers. Viral loads of breakthrough Delta variant infection cases were 251 times higher than those of cases infected with old strains detected between March-April 2020. Time from diagnosis to PCR negative was 8–33 days (median: 21). Neutralizing antibody levelsafter vaccination and at diagnosis of the cases were lower than those in the matched uninfected controls. There was no correlation between vaccine-induced neutralizing antibody levels and viral loads or the development of symptoms.
Interpretation:
Breakthrough Delta variant infections are associated with high viral loads, prolonged PCR positivity, and low levels of vaccine-induced neutralizing antibodies, explaining the transmission between the vaccinated people. Physical distancing measures remain critical to reduce SARS-CoV-2 Delta variant transmission.
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Data collection:
We collected demographics, vaccination history and clinical data alongside the results of SARS-CoV-2 PCR diagnosis from the study participants. For SARS-CoV-2 antibody measurement, we obtained 2ml of EDTA plasma from each study participants at diagnosis and at week 1, 2 and 3 after admission. Nasopharyngeal-throat swab collection, PCR testing and viral load conversion Nasopharyngeal swabs were collected and placed in 1mL of viral transport medium, and
200uL was used for viral RNA extraction using the MagNApure 96 platform (Roche Diagnostics, Germany), according to the manufacturer’s instructions. For SARS-CoV-2 RNA detection, we used real-time RT-PCR assay with primers and probe targeted at the envelope protein-coding gene (TIB MOLBIOL)7. PCR Ct values were converted to RNA loads using an in-house established formula (y = -0.3092x + 12.553, R² = 0.9963, where y is viral load and x is Ct value) based on 10-fold dilution series of in-vitro transcribed RNA.
Whole genome sequencing and sequence analysis:
Whole-genome sequences of SARS-CoV-2 were directly obtained from leftover RNA after PCR testing using ARTIC protocol and Illumina reagents on a MiSeq platform with the inclusion of a negative control in every sequencing run. The obtained reads from individual samples were mapped to a SARS-CoV-2 reference genome (GISIAD sequence ID: EPI_ISL_1942165) to generate the consensuses using Geneious software (Biomatter, New Zealand). SARS-CoV-2 variant assignment was carried out using Pangolin.9 Detection of amino acid changes as compared to the original Wuhan strain was done using COV-GLUE.10 Maximum likelihood phylogenetic tree was reconstructed using IQ-TREE.
A deadly experiment...
But seriously I'm not sure
Findings:
Between 11th–25th June 2021 (week 7–8 after dose 2), 69 healthcare workers were tested positive for SARS-CoV-2. 62 participated in the clinical study. were (pre)symptomatic with one requiring oxygen supplementation. All recovered uneventfully. 23 complete-genome sequences were obtained. They all belonged to the Delta variant, and were phylogenetically distinct from the contemporary Delta variant sequences obtained from community transmission cases, suggestive of ongoing transmission between the workers. Viral loads of breakthrough Delta variant infection cases were 251 times higher than those of cases infected with old strains detected between March-April 2020. Time from diagnosis to PCR negative was 8–33 days (median: 21). Neutralizing antibody levelsafter vaccination and at diagnosis of the cases were lower than those in the matched uninfected controls. There was no correlation between vaccine-induced neutralizing antibody levels and viral loads or the development of symptoms.
Interpretation:
Breakthrough Delta variant infections are associated with high viral loads, prolonged PCR positivity, and low levels of vaccine-induced neutralizing antibodies, explaining the transmission between the vaccinated people. Physical distancing measures remain critical to reduce SARS-CoV-2 Delta variant transmission.
...
Data collection:
We collected demographics, vaccination history and clinical data alongside the results of SARS-CoV-2 PCR diagnosis from the study participants. For SARS-CoV-2 antibody measurement, we obtained 2ml of EDTA plasma from each study participants at diagnosis and at week 1, 2 and 3 after admission. Nasopharyngeal-throat swab collection, PCR testing and viral load conversion Nasopharyngeal swabs were collected and placed in 1mL of viral transport medium, and 200uL was used for viral RNA extraction using the MagNApure 96 platform (Roche Diagnostics, Germany), according to the manufacturer’s instructions. For SARS-CoV-2 RNA detection, we used real-time RT-PCR assay with primers and probe targeted at the envelope protein-coding gene (TIB MOLBIOL)7. PCR Ct values were converted to RNA loads using an in-house established formula (y = -0.3092x + 12.553, R² = 0.9963, where y is viral load and x is Ct value) based on 10-fold dilution series of in-vitro transcribed RNA.
Whole genome sequencing and sequence analysis:
Whole-genome sequences of SARS-CoV-2 were directly obtained from leftover RNA after PCR testing using ARTIC protocol and Illumina reagents on a MiSeq platform with the inclusion of a negative control in every sequencing run. The obtained reads from individual samples were mapped to a SARS-CoV-2 reference genome (GISIAD sequence ID: EPI_ISL_1942165) to generate the consensuses using Geneious software (Biomatter, New Zealand). SARS-CoV-2 variant assignment was carried out using Pangolin.9 Detection of amino acid changes as compared to the original Wuhan strain was done using COV-GLUE.10 Maximum likelihood phylogenetic tree was reconstructed using IQ-TREE.